1. Field of the Disclosure
The present disclosure relates generally to detecting synchronization in a wireless communication system, and more particularly, to a method and an apparatus for detecting synchronization in a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) system.
2. Description of the Related Art
TD-SCDMA technology is obtained by combining Time Division Duplexing (TDD) and Time Division Multiple Access (TDMA) technology with Synchronous CDMA technology. Accordingly, TD-SCDMA technology has unique advantages, such as flexible frequency allocation, implementation of a low-priced transmitter/receiver, evolution of a network from Global System for Mobile communications (GSM), and the like, as compared with other 3G technologies such as Wideband Code Division Multiple Access (WCDMA) and CDMA2000.
In CDMA, which is robust against multipath fading and interference, cells can be distinguished from each other by using a midamble code and a chip-level scramble code. A midamble code is a channel training sequence used for channel estimation, whereas a chip-level scramble code is used to scramble transmission code symbols so that transmission symbols may be close to white Gaussian noise.
Also, when a TD-SCDMA system is an intra-frequency network, cell recognition or synchronization detection may be implemented by SYNC_DL (a downlink synchronization code) in a downlink pilot time slot and midamble codes. Further, users of different cells can be recognized by a scramble code and a midamble code.
However, when intra-frequency interference exists in a TD-SCDMA system, the TD-SCDMA system uses a SYNC_DL (the downlink synchronization code) in the downlink pilot time slot, a midamble code, and the like, which may be interfered with by other adjacent cells.
In other words, in an environment in which multiple cells use an identical frequency, while a synchronization code transmitted through a midamble code and a pilot time slot is broadcast by a serving cell and adjacent cells, the relevant cell may be affected by other midamble codes or synchronization codes broadcast by the adjacent cells.
A receiver may independently estimate a channel and detect synchronization by using signals received from multiple adjacent cells. Such a method for estimating a channel and detecting synchronization may cause interference to the estimated channel response signal and the synchronization detection signal. In the worst case, due to the interference, the receiver may fail to detect the synchronization.